How to have multiple animations in a blender file, with a multiobject mesh without a rig
Using a rig is the best way, expecially for exporting to Unity. It lets you also join all the meshes into one and still be able to control each part individually with a serie of separate actions.
This kinds of rigs are very simple, just create in edit mode a bone for every piece, orient them in the same way as Unity's world coordinates for easier editing.
Establish any parent-child relation you need, and create a root bone which will be the parent of every other branch of bones.
Then select the mesh, shift select the armature, press Ctrl P and choose &quot;with empty groups&quot;.
Then select the mesh, enter edit mode select all vertices of a piece (shortcut L), select the relevant vertex group/bone and click assign weight 1.0.
Repeat for every piece.
Don't use &quot;with automatic weights&quot;, as the pieces are not supposed to deform.
Don't forget to Apply (Ctrl A) all transformations of mesh and armature before rigging.